Coded data generation or conversion – Analog to or from digital conversion – Analog to digital conversion
Patent
1995-10-16
1997-11-04
Gaffin, Jeffrey A.
Coded data generation or conversion
Analog to or from digital conversion
Analog to digital conversion
12866001, A61B 800
Patent
active
056844840
DESCRIPTION:
BRIEF SUMMARY
(TECHNICAL FIELD)
The present invention relates to a method and apparatus for multi-channel digital reception and an apparatus of ultrasonic diagnosis, and more particularly to a method and apparatus for multi-channel digital reception and an apparatus of ultrasonic diagnosis based on the digital processing for obtaining common-phase components and orthogonal components from analog reception signals originating from a signal source and arriving on multiple channels by way of different transfer routes.
(BACKGROUND ART)
FIG. 8 is a block diagram of an example of conventional apparatus of ultrasonic diagnosis.
In this ultrasonic diagnostic apparatus 101, a probe 2 which receives a ultrasonic echo signal delivers analog reception signals from its multiple channels, and the signals are converted into digital data D1-Dx by A/D converters 31-3x. Next, the digital data D1-Dx are rendered the orthogonal detection by orthogonal detection circuits 1061-106x of channel 1 through channel x so that channel common-phase components I1'-Ix' and channel orthogonal components Q1'-Qx' are extracted. Next, the extracted components are delayed by delay circuits 41i-4xq so that the difference of propagation times of the ultrasonic echo among the channels is nullified. Next, the delayed channel common-phase components I1-Ix are summed by a summing circuit 7I to obtain a composite common-phase component I, and the delayed channel orthogonal components Q1-Qx are summed by a summing circuit 7Q to obtain a composite orthogonal component Q. A DSC (Digital Scan Converter) produces a Doppler image or color flow mapping image from the composite common-phase component I and composite orthogonal component Q, and the image is displayed by a display device 9.
There is known "digital phase apparatus" described in Japanese patent publication JP-A-Hei-5-184568 as a pertinent prior art. However, this patent publication does not disclose at all the technique related to the orthogonal detection.
FIG. 9 is an explanatory diagram showing that a ultrasonic continuous wave emitted by the probe 2 is reflected at point P and a resulting reflected ultrasonic echo is received by channel X and channel Y.
The ultrasonic echo at point P is assumed to be expressed as follows: the traveling distance Dy to the channel Y, the reception signal of channel X is:
These signals are rendered the orthogonal detection by using the reference signals cos(2.pi.f.sub.0 t) and sin(2.pi.f.sub.0 t), and the orthogonal detection circuit produces outputs:
In the operation of digital orthogonal detection, digital data at prescribed sampling points are taken thereby to obtain the above-mentioned common-phase components Ix'(t) and Iy'(t) and orthogonal components Qx'(t) and Qy'(t), as will be explained later.
The delay circuits delay the signals so that the difference of the propagation time of the P-X route and the propagation time of the P-Y route is nullified as follows. ##EQU1## The comparison of the above Ix(t) and Iy(t) reveals that they are consistent in the time factor in the term of amplitude, but they are out of phase. The comparison of the above Qx(t) and Qy(t) reveals that they are consistent in the time factor in the term of amplitude, but they are out phase.
Namely, the procedure of the orthogonal detection first by using the reference signals cos(2.pi.f.sub.0 t) and sin(2.pi.f.sub.0 t), and the delay operation next cannot achieve the phase-matched summation.
Otherwise, when the following reference signals are used for the orthogonal detection of channel X:
Namely, by making the digital data sampling clock to have different phases among the channels, or by making digital orthogonal detection to have different sampling points among the channels, phase-matched summation is made possible.
In this case, however, sampling clocks of multiple phases are needed and the digital orthogonal detector becomes complex.
Digital orthogonal detection necessitates sampling points of at least four times the carrier frequency, and therefore in the case of a constant sampling rate fs,
REFERENCES:
patent: 5027821 (1991-07-01), Hirama et al.
Gaffin Jeffrey A.
GE Yokogawa Medical Systems Limited
Jean-Pierre Peguy
Kojima Moonray
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